[c-nsp] 7609 DHCP alternatives - EVC / Subinterfaces

Arie Vayner (avayner) avayner at cisco.com
Sat Oct 24 11:19:35 EDT 2009


Victor,

Use the EVC alternative.
It would allow you to get the flexibility offered by EVC with regards to
VLAN number space, L2 services scalability, QOS and many other advanced
capabilities.

Arie

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Victor Lyapunov
Sent: Tuesday, October 20, 2009 09:54
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] 7609 DHCP alternatives - EVC / Subinterfaces

Hi All

I am trying to test DHCP functionality with 7600 router. Traffic
arrives from all customer facing interfaces (ES+), arrive using the
same VLAN. 7600 perfoms DHCP relay and acts as a gateway for all of
them. With the new cards ES+ we have two options for the configuration
of customer facing interfaces

1. Using EVC + SVI interface

  int g4/1
     service instance 100 ethernet
     encapsulation dot1q 100
     rewrite ingress tag pop 1 symmetric
     bridge-domain 100 split-horizon
  int g4/2
     service instance 100 ethernet
     encapsulation dot1q 100
     rewrite ingress tag pop 1 symmetric
     bridge-domain 100 split-horizon

  int Vlan 100
     ip address 10.0.0.1 255.255.255.0
     ip helper address 192.168.0.1

2. Using IP subinterfaces

  int loopback 100
     ip address 10.0.0.1 255.255.255.0

  int g4/1.100
     encapsulation dot1q 100
     ip address unnumbered loopback 100
     ip helper address 192.168.0.1

  int g4/2.100
     encapsulation dot1q 100
     ip address unnumbered loopback 100
     ip helper address 192.168.0.1


Both configurations seem to achieve the same effect but I am not sure
which one
is the preferable for large amount of traffic / subscribers.

For example due to the bridge domain I would expect that the first
alternative will
create more entries in the mac-address table.

Thanx

Victor
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